package com.test.thread.countDownLatch;

/**
 CountDownLatch类是一个同步计数器,构造时传入int参数,该参数就是计数器的初始值，每调用一次countDown()方法，计数器减1,计数器大于0 时，await()方法会阻塞程序继续执行
 CountDownLatch如其所写，是一个倒计数的锁存器，当计数减至0时触发特定的事件。利用这种特性，可以让主线程等待子线程的结束。下面以一个模拟运动员比赛的例子加以说明。
 */
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class CountDownLatchDemo {
	private static final int PLAYER_AMOUNT = 5;

	public CountDownLatchDemo() {
		// TODO Auto-generated constructor stub
	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		// 对于每位运动员，CountDownLatch减1后即结束比赛
		CountDownLatch begin = new CountDownLatch(1);
		// 对于整个比赛，所有运动员结束后才算结束
		CountDownLatch end = new CountDownLatch(PLAYER_AMOUNT);
		Player[] plays = new Player[PLAYER_AMOUNT];

		for (int i = 0; i < PLAYER_AMOUNT; i++)
			plays[i] = new Player(i + 1, begin, end);

		// 设置特定的线程池，大小为5
		ExecutorService exe = Executors.newFixedThreadPool(PLAYER_AMOUNT);
		for (Player p : plays)
			exe.execute(p); // 分配线程
		System.out.println("Race begins!");
		begin.countDown();
		System.out.println("begin: " + begin.getCount());
		try {
			end.await(); // 等待end状态变为0，即为比赛结束
		} catch (InterruptedException e) {
			// TODO: handle exception
			e.printStackTrace();
		} finally {
			System.out.println("Race ends!");
		}
		exe.shutdown();
	}
}